Implant retention, detachment, and delivery system

ABSTRACT

A medical implant delivery system is described. The system can be used to deliver a variety of implants including stents and/or stent grafts. The delivery system retains the implant during delivery and detaches the implant at a target location.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/268,271 filed Sep. 16, 2016 entitled Implant Retention, Detachment,And Delivery System, which claims benefit of and priority to U.S.Provisional Application Ser. No. 62/220,905 filed Sep. 18, 2015 entitledImplant Retention, Detachment, And Delivery System, and of U.S.Provisional Application Ser. No. 62/222,063 filed Sep. 22, 2015 entitledImplant Retention, Detachment, And Delivery System, all of which arehereby incorporated herein by reference in their entireties.

BACKGROUND OF THE INVENTION

Medical implants such as stents are sometimes used to open blood vesselsto mitigate the effects of plaque buildup, to prevent embolic materialwithin an aneurysm from escaping, as a flow diverter to limit blood flowto certain regions, or for other reasons. These implants can bedelivered via an implant delivery system in which an elongated pusher isused to push the implant through a catheter or sheath to a treatmentsite.

Delivering implants such as stents can be a challenge since manydelivery systems do not allow the implant to be repositioned after itsinitial deployment. Therefore, if the implant is initially deployed toan undesirable location, the physician is without recourse to adjust theimplant's deployed position. Hence, there is a need for an implantdelivery system that provides repositionability of an implant, as wellas a reliable release structure to deploy the implant.

SUMMARY OF THE INVENTION

An implant delivery system is described. The implant delivery system canbe used for a stent, stent-graft, embolic coils, plugs, occluders, orother implants.

In one embodiment, an implant delivery system comprises an implant and aretention structure.

In another embodiment, an implant delivery system comprises an implantand a retention structure. The retention structure is disposed on adistal portion of an elongated pusher and is composed of a mesh or alooped structure.

In another embodiment, an implant delivery system comprises an implantand a retention structure. The implant is affixed to said retentionstructure.

In another embodiment, an implant delivery system comprises an implantand a retention structure. The retention structure includes elements togrip the implant.

In another embodiment, an implant delivery system comprises an implantand a retention structure in which the retention structure separatesfrom the implant and remains with the delivery system after the implantafter the implant is detached from the delivery system.

In another embodiment, an implant delivery system comprises an implant,retention structure, and one or more tethers.

In another embodiment, an implant delivery system comprises an elongatedpusher member having a retention structure disposed on a distal portionof the pusher member and engaged with an implant. The pusher, retentionstructure, and implant are disposed within a catheter or sheath and canbe advanced out of a distal end of the catheter. The retention structurecan be a conical mesh that is positioned around a proximal end of theimplant. The retention structure can also be a plurality of loopsdisposed around a proximal end of the implant or positioned throughloops on the implant. The implant may be further connected to the pushervia one or more tethers that can be broken via a mechanism located atleast partially within the pusher.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects, features and advantages of which embodiments ofthe invention are capable of will be apparent and elucidated from thefollowing description of embodiments of the present invention, referencebeing made to the accompanying drawings, in which:

FIG. 1 illustrates an example embodiment of a woven stent that can beused with the delivery system of the present invention.

FIG. 2 illustrates an example embodiment of a woven, dual-layer stentthat can be used with the delivery system of the present invention.

FIG. 3 illustrates a side view of an embodiment of a delivery systemwith a mesh or woven retaining structure.

FIGS. 4 and 5 illustrate side views of the delivery system of FIG. 3 invarious states of deployment.

FIG. 6 illustrates a side view of another embodiment of a deliverysystem with a mesh or woven retaining structure and a tether.

FIG. 7 illustrates a side view of a pusher that can be used withdifferent embodiments of the present invention.

FIG. 8 illustrates a side view of another embodiment of a deliverysystem with a plurality of loops that comprise the retaining structure.

FIG. 9 illustrates a side view of a pusher and the looped retainingstructure of FIG. 8 .

DESCRIPTION OF EMBODIMENTS

Specific embodiments of the invention will now be described withreference to the accompanying drawings. This invention may, however, beembodied in many different forms and should not be construed as limitedto the embodiments set forth herein; rather, these embodiments areprovided so that this disclosure will be thorough and complete, and willfully convey the scope of the invention to those skilled in the art. Theterminology used in the detailed description of the embodimentsillustrated in the accompanying drawings is not intended to be limitingof the invention. In the drawings, like numbers refer to like elements.

U.S. Pat. Nos. 8,182,506, 8,192,480, 8,460,332; and U.S. Pub. Nos.US20060200192, US20090062812, US20090163780, US20100268204,US20110301686, US20150289879, are hereby incorporated by reference intheir entireties. These references disclose implant detachment systemsthat can be used in conjunction with the implant delivery systemembodiments described herein. These references generally disclose athermal detachment system in which a tether connects to an implant andis selectively broken by activating a heater coil to cause implantdeployment.

The present invention is generally directed to an implant deliverysystem having an implant retention structure that can improve deploymentof an implant, as well as retrieve an implant that has not been fullydeployed. The implant retention structures of the present invention areparticularly useful for deploying and repositioning stents, such asthose shown in FIGS. 1 and 2 , and described in greater detail below.

FIG. 1 illustrates a stent 1 that is woven or braided together from oneor more wires 2 to form a generally cylindrical shape with a pluralityof loops 4 around the perimeter of both ends of the stent 1. The ends ofthe wires 2 can be connected to each other via welding, bonding agents,or a similar adhesive mechanism. Once the ends are welded or bonded, thewire 2 has no “free” ends.

Each of the loops 4 may contain one or more coil members 6. Preferably,the coil members 6 are disposed around the wire 2 of the loops 4 and arecomposed of radiopaque material to indicate the proximal and distal endsof the stent 1. Additionally, these coil members 6 may provideadditional anchoring force within a delivery device, as described ingreater detail below.

In one example, a distal end of the stent 1 includes at least two loops4 with two coil members 6 each and a proximal end of the stent 1includes at least two loops 4 with one coil member 16 each. However, itshould be understood that the stent 1 can include any number of coilmembers 6 on any number of loops 4.

Preferably, these coil members 6 are positioned near a center area ofthe loop 4, such that when the stent 1 is in a collapsed state, the coilmembers 6 are positioned near the very distal or very proximal end ofthe stent 1.

Preferably, each coil member 6 is composed of a tantalum wire 5 woundaround a portion of the loop 4. Each coil member 6 can be composed of adiscrete tantalum wire 5 or a single tantalum wire 5 can form multiplecoil members 6 (as seen in FIG. 1 ). As seen in FIG. 1 , the wire 5 canconnect to coil members 6 on each end of the stent 100 by being locatedwithin the inner portion or lumen of the stent 1. Alternately, the wire5 may be woven into the wires 2 of the stent 1.

One specific technique for minimizing the exposure of the distal coils 6during retraction is to weave the stent 1 such that portions of the wire2 overlap (i.e., are positioned at a greater outer diameter position)than the side of the loop 4 with coil 6. Some smaller, minor loops 7 arewoven to overlap a first side of the loop 4 that includes the coil 6while other minor loops 7 are woven underneath a second side of the loop4.

FIG. 2 illustrates a preferred embodiment of a dual layer stent 20according to the present invention. Generally, the dual layer stent 20includes an outer anchoring stent 1 that is similar to the previouslydescribed stent 1 seen in FIG. 1 . The dual layer stent 20 also includesan inner flow-diverting layer 22 that is disposed within the inner lumenor passage of the anchoring stent 1. The inner flow-diverting layer 22is preferably made from a wire 24 to form a mesh type structure.

The proximal end of the dual layer stent 20 includes a plurality ofattachment members 26 that connect the anchoring stent 1 with theflow-diverting layer 22. The attachment members 26 can be composed oftantalum wire (in this case is 0.001″ dia.) and can be attached toportions of wire 2 and wire 24. In another embodiment, the proximal endof the flow-diverting layer 22 can be crimped on to the wires 2 of theanchoring stent 1. In another embodiment, portions of the stent 1 andflow-diverting layer 22 can be woven through each other for attachmentpurposes.

Additional details of each stent 1 and 20 can be found in U.S. Pub. No.2013/0245745, which is hereby incorporated herein by reference in itsentirety.

FIG. 3 illustrates one embodiment of an implant delivery system 100having an elongated pusher 110 and a retention structure 102 thatextends from a distal portion of the pusher 110. The pusher 110, theretention structure 102, and the stent 1 (or alternately another implantdevice) are positioned within a catheter 112 such that at least aportion of the retention structure 102 overlaps a proximal portion ofthe stent 1. The catheter 112 prevents the retention structure 102 andstent 1 from expanding from their radially compressed configurationprior to deployment.

Referring to FIGS. 4 and 5 , as the pusher 110 is advanced towards adistal end of the catheter 112, the retention structure 102 distallyopens into a conical shape, thereby allowing the stent 1 to similarlyopen. If the location of the stent 1 inside the patient is undesirable,the pusher 110 and the attached retention structure 102 can beproximately withdrawn back into the catheter 112, causing the stent 1 tosimilarly be compressed and withdrawn back into the catheter 112 forrepositioning and redeployment. The retention structure 102 allows forretraction of the stent 1 even after the stent 1 is completely outsidethe catheter 112. This is important because until the stent 1 iscompletely outside the catheter 112, the exact position of the stent 1and the true length of stent 1 after foreshortening is not known. Theretention structure 102 allows for greater opportunity for exactplacement of the stent 1, since the physician will have a moreopportunity to reset the stent 1 to the desired location if the initialdeployment of the stent 1 is not ideal.

In one embodiment, the retention structure 102 is a mesh tubular shapeformed from one or more braided or woven wires (e.g., Nitinol wires).Alternately, the mesh can be formed from laser cutting or etching asolid tubular structure. The proximal end of the retention structure 102is fixed or mounted to a distal portion of the pusher 110 via welding,adhesive, a mechanical fixture, or any combinations of these methods.

Retention structure 102 may also include one or more engagement elements106 fixed to its mesh 104 to assist the retention structure 102 inengaging the stent 1. The engagement elements 106 can take the form ofpolymeric or metallic protrusions that are one or more of the followingshapes: spherical, elliptical, oval, pyramidal, rectangular, conical,truncated cone, truncated pyramid, square, or similar shapes. Theseengagement elements 106 can be attached via adhesive, wire or fiberties, or welding, such that they protrude radially inwardly from theretention structure 102. The engagement elements 106 are sized andpositioned on the mesh 104 so as to at least partially fit within gapsin the stent 1. For example, the engagement elements 106 may align withthe end loops 4, minor loops 7, or the gaps formed between the wovenwires of the stent 1. In this respect, when the retention structure 102and stent 1 are radially compressed within the catheter 112 (or deliverysheath), the engagement elements 106 prevent the stent 1 from lateral oraxial movement within the catheter 112, preventing the stent 1 fromescaping until the retention structure 102 is exposed and radiallyexpanded.

The retention structure 102 in FIG. 3 is illustrated with a trumpeted orconical distal portion which may be useful to ensure the stent 1 islocked down or engaged during delivery and deployment. Prior toconnection to the pusher 110, the mesh 104 can be heat-set to form aradially-expanded tubular shape, so that once the proximal end of themesh 104 is connected to the pusher 110, the mesh 104 expands to theconical shape. Alternately, the mesh 104 can be heat-set to form atrumpeted/conical shape prior to its connection to the pusher 110. Inanother alternate embodiment, the mesh 104 can be heat-set to form aconical shape having an abrupt inward taper at its distal end to act asa hook or circular ridge against the stent 1. In another alternateembodiment, the mesh 104 can form an undulating shape that increases anddecreases in diameter along its length.

In the embodiment of the delivery system 100 of FIGS. 2-5 , the pusher110 can be an elongated member that is sufficiently flexible to advancethrough a patient's vascular system, while also maintaining sufficientpushability to push the retention structure 102 and stent 1 out of thecatheter 112.

Referring to FIGS. 2-5 , in operation, the distal end of the catheter112 is advanced to a target treatment location (or adjacent thatlocation) within a patient's vascular system. This positioning can beachieved by first advancing a guidewire so that the guidewire's distalend is located at or near the target treatment location. A deliverysheath can be advanced over the guidewire so that its distal end islocated at the target treatment location, or the catheter 112 canadvanced over the guidewire without the use of a delivery sheath.Several different techniques of positioning a catheter within thevasculature of a patient are known in the art and can be used with theembodiments of the present invention.

Once the distal end of the catheter 112 is located at a desiredlocation, the pusher 110 is advanced distally. As seen in FIG. 4 , adistal portion of the stent 1 is advanced out of the catheter 112 andbegins to radially expand. As the stent 1 continues to advance distally,the retention structure 102 also advances distally out of the catheter112, maintaining at least a portion of the proximal end of the stent 1in a radially compressed (or partially compressed) configuration,despite being fully outside of the catheter 112.

If the distal portion of the stent 1 has not deployed to the desiredtarget location in the vessel, the pusher 110 can be withdrawnproximally by the physician. As the retention structure 102 iswithdrawn, it radially compresses, thereby compressing the proximal endof the stent 1 so as to allow it to reenter the lumen of the catheter112. The engagement elements 106 help the retention structure 102 tograsp and pull the stent 1, ensuring that the stent 1 does not slip outof the retention structure 102. Once a portion of the stent 1 hasreentered the catheter 112, the remaining portion of the stent 1 canalso be withdrawn into the catheter 112, as well.

Finally, the catheter 112 is repositioned and the pusher 110 is advanceddistally to deploy the stent 1 as previously described. Once theretention structure 102 has been sufficiently advanced out of thecatheter 112, as seen in FIG. 5 , it radially expands to a sufficientsize so as to disengage with the stent 1. The pusher 110 and retentionstructure 102 are proximally withdrawn into the catheter 112 and thecatheter 112 is withdrawn from the patient.

FIG. 6 illustrates another embodiment of a delivery system 120 that isgenerally similar in structure and function to the delivery system 100that has been previously described. However, the delivery system 120further includes a tether 122 that is connected to the pusher 110 andcan be selectively released from the stent 1 when fully deployed in adesired target location. The tether 122 can be a single filament that isfixed to both the pusher 110 and attached to the proximal loops of thestent 1 (e.g., via adhesive, mechanical ties, or welding). The tetheringfeature described in FIG. 6 (and alternatively in FIGS. 8 and 9 ) may beused in conjunction with the retention structure 102 or in lieu of theretention structure 102.

FIG. 7 illustrates an embodiment of a pusher 110 of FIG. 6 , thatillustrates the disconnect function. As seen in FIG. 7 , the stent 1 isconnected to the pusher 110 via a tether 122 and can be selectivelyactivated to break the tether 122 to release the stent 1. Morespecifically, a resistance heater coil 130 is connected to electricalwires 131 and 132 that selectively supply power from a proximal powersource. As the power is supplied, the heater coil 130 heats up, breakingthe tether 122. An insulating cover 134 and reinforcement ring 136 aredisposed on the outer portion of the pusher 110 to thermally isolate andreinforce the structure of the pusher 110.

In the embodiment of FIG. 7 , the tether 122 extends through aproximally directed coil portion 138 and coil 140 of the stent 1, and isfurther adhered via adhesives 140. However, the tether 122 may alsoattach at both of its ends to the pusher 110, forming a loop around oneor more of the end loops 4 of the stent 1.

FIG. 8 illustrates another embodiment of a pusher 110 having a retentionstructure 150 composed of a plurality of loops 152. The loops 152 canpress against an outer surface of each of the end loops 4 to helpmaintain the proximal portion of the stent 1 in a compressedconfiguration similar to that described for the retention structure 102.Alternately, each of the loops 152 can be positioned through each of thestent loops 4 or 7.

If the loops 152 are positioned on the outside of the stent loops 4(i.e., not through the loops 4), the delivery method is similar to thatof the delivery system 100 shown in FIGS. 4 and 5 . If the loops 152 arepositioned through the stent loops 4 (i.e., in a “chain-like”interlocking manner), the delivery method is similar to that of thedelivery system 120 of FIG. 6 , with regard to the detachment shown inFIG. 7 .

While the retention structure 150 is illustrated with three loops 152,different numbers of loops 152 can be used, such as 2, 4, 5, 6, 7, 8, 9,or 10. In one embodiment, the number of loops 152 is equal to the numberof stent loops 4 on the end of the stent 1. In another embodiment, oneor more of the loops 152 can pass through more than one stent loop 4.

If the loops 152 are positioned on the outside of the stent loops 4(i.e., not through the loops 4), they may be composed of a shape memoryalloy. If the loops 152 are positioned through the stent loops 4 (i.e.,in a “chain-like” interlocking manner), the loops 152 are preferablycomposed of a polymer that can be detached or broken by a mechanism inthe pusher 110. For example, the pusher 110 may be that shown in FIG. 7and therefore is configured to generate heat to break at least onestrand or location along the loop 152.

As seen in FIG. 9 , the loops 152 can also each have two free ends(i.e., is initially a linear configuration) that are both fixedinternally to the pusher 110 or can initially be complete loop filamentsin which a single location on the loop is fixed within the pusher 110.In the arrangement with two free ends (i.e., a linear strand),preferably only one end portion or section of each of the strand of theloops 152 passes through the heater coil 130 while a portion at theopposite end of the strand is positioned outside of the heater coil 130.The strand may also pass through an insulating sleeve 160 positionedadjacent the heater coil 130 to thermally isolate it from heat generatedby the heater coil 130. In this respect, once the loop 152 is severed,the remaining portions of the strands of the loops 152 remain connectedto the pusher 110 after breakage by the heater coil 130 and the stentloops 4 are released from the pusher 110.

Other embodiments of the pusher 110 utilize a multiple lumen structurein which the heater coil 130 and a first portion of the loop 152 arelocated within one inner lumen and a second portion of the loop 152 islocated in a separate outer lumen. This separate lumen would prevent thesecond portion of loop 152 from having any contact with the heater coil130.

Additional embodiments may utilize multiple loop structures, such as onedelivery loop 152 which grasps all the stent loops 4 as well asseparate, individual delivery loops 152 which grasp only one stent loop4. Additional variations may use fewer delivery loops 152 than the totalnumber of stent loops 4 provided. Thus, for example, three stent-loops 4are used with two delivery loops 152. In another example, one deliveryloop 152 engages two stent loops 4 and the other delivery loop 152engages only one stent loop. Additional embodiments may use multipleloop structures 152 for each stent loop 4 (e.g., two delivery loops 152to snare each stent loop 4) in order to further augment retention.Variations are also possible in which combinations of each of thevarious embodiments described are used (e.g., some stent loops 4 utilizemultiple delivery loops 152, some stent loops 4 utilize only onedelivery loop 152, and some delivery loops 152 grasp multiple stentloops 4).

It should be understood that elements or aspects from the variousembodiments presented herein can be combined in a wide array ofdifferent configurations. For example, one embodiment may utilize acombination of a mesh retention structure 102, a delivery loop retentionstructure 150, and a tether 122 to further enhance the retentioncapabilities of the implant delivery system.

The presence of one or more tethers 122 may not necessarily prevent theexpansion of the stent 1 after exiting the catheter 112, since stents 1generally have a strong shape memory and quickly adopt their expandedstate upon delivery. However, if the tether 122 was in sufficiently hightension, the tensile force of the tether 122 may keep the proximalportion of the stent 1 from expanding, and thus keep the stent 1connected to the retention structure 102. A spring, coil, or tube can beused to keep the tether 122 in a tensioned state to further augment thetensile force of the tether 122.

With regard to embodiments utilizing one or more tethers 122, delayingthe tether 122 detachment until after the stent 1 has fully expanded mayallow the stent 1 to be repositionable while the tether(s) 122 areattached, since the tether(s) 122 connect the stent 1 to the deliverypusher 110 (some additional variables might still impactrepositionability such as the size/weight of the stent 1 and thenarrowness of the vessel). Once the retention structures 102 and tethers122 are detached, the stent 1 is detached from the pusher 110 entirelyand is likely not repositionable after this point.

The delivery system embodiments described can be used to deliver one ormore implants such as stents, stent grafts, embolic coils, occluders,plugs, and similar devices. While the example of a stent was describedin the embodiments of this specification, any of these other implantsmay similarly be used. For example, to deliver an embolic coil, the meshretention structure 102 supports the proximal portion of an embolic coilfor releasable delivery. The proximal part of an embolic coil may have areceiving structure to accommodate the engagement elements 106 of theretention structure 102. Other implants may also include a loopstructure 4 at a proximal region of those implants.

Any figures shown and/or described are not meant to be limitedexclusively to the representation of what is shown and instead areillustrative in nature. Similarly, any measurements and/or descriptionsof materials are meant to be representations, approximations, andexamples rather than being expressly limiting.

Although the invention has been described in terms of particularembodiments and applications, one of ordinary skill in the art, in lightof this teaching, can generate additional embodiments and modificationswithout departing from the spirit of or exceeding the scope of theclaimed invention. Accordingly, it is to be understood that the drawingsand descriptions herein are proffered by way of example to facilitatecomprehension of the invention and should not be construed to limit thescope thereof.

What is claimed is:
 1. A delivery system for an implant, comprising: anelongated pusher having a distal end and a proximal end; a retentionstructure comprising a plurality of loops that are each connected at thedistal end of the elongated pusher and that extend distally away fromthe elongated pusher; and, an implant located near the distal end of theelongated pusher; wherein the plurality of loops engages the implant;wherein the implant is a stent having a plurality of stent openings;wherein each of plurality of loops are positioned through one of theplurality of stent openings; and, wherein each of the plurality of loopsare composed of a polymer configured to break upon application of heat.2. The delivery system of claim 1, wherein each of the plurality ofloops have a radially compressed position and a radially expandedposition.
 3. The delivery system of claim 2, wherein each of theplurality of loops press against an outer surface of a proximal end ofthe implant when the plurality of loops is in the compressed position.4. The delivery system of claim 3, wherein the retention structurefurther comprises a heater coil in the pusher.
 5. The delivery system ofclaim 1, wherein each loop of the plurality of loops has two free endsthat are both fixed internally to the pusher.
 6. The delivery system ofclaim 1, wherein each loop is a circular ring of wire and wherein asingle location of the circular ring of wire is located within thepusher.
 7. The delivery system of claim 1, wherein the pusher furthercomprises a heater coil.
 8. The delivery system of claim 7, furthercomprising an insulating sleeve positioned adjacent the heater coil inthe pusher.
 9. The delivery system of claim 8, wherein each of theplurality of loops has two ends that are separately attached within thepusher, and wherein each of the plurality of loops is positioned throughboth the heater coil and the insulating sleeve, such that activation ofthe heater coil breaks each of the plurality of loops at only thelocation of the heater coil.
 10. A delivery system for an implant,comprising: an elongated pusher having a distal end and a proximal end;a retention structure comprising a plurality of loops that are eachconnected at the distal end of the elongated pusher and that extenddistally away from the elongated pusher; and, an implant located nearthe distal end of the elongated pusher; wherein the plurality of loopsengages the implant; and, wherein the retention structure furthercomprises a mesh having a tubular compressed shape and a conicalexpanded shape that opens distally toward the implant.
 11. A deliverysystem for an implant, comprising: an elongated pusher having a distalend and a proximal end; a plurality of loops composed of a shape memoryalloy and that are each connected at the distal end of the elongatedpusher, extending distally away from the elongated pusher; the pluralityof loops having a radially compressed configuration and a radiallyexpanded configuration; a stent located near the distal end of theelongated pusher; and, a mesh having a tubular compressed shape and aconical expanded shape that opens distally toward the implant; whereinthe plurality of loops radially press against a proximal end of thestent when in the radially compressed configuration and release thestent when in the radially expanded configuration.
 12. A delivery systemfor an implant, comprising: an elongated pusher having a distal end anda proximal end; a plurality of loops composed of a shape memory alloyand that are each connected at the distal end of the elongated pusher,extending distally away from the elongated pusher; the plurality ofloops having a radially compressed configuration and a radially expandedconfiguration; and, a stent located near the distal end of the elongatedpusher; wherein the plurality of loops radially press against a proximalend of the stent when in the radially compressed configuration andrelease the stent when in the radially expanded configuration; and,wherein the stent has a plurality of end loops extending from a proximalend of the stent, and the plurality of loops composed of shape memoryare engaged with the plurality of end loops of the stent.
 13. Thedelivery system of claim 12, wherein each of the plurality of loopscomposed of shape memory is engaged with one of the plurality of endloops of the stent.